1. Field
The disclosed concept pertains generally to acoustic noise induced by electrical conductivity faults and, more particularly, to acoustic sensor systems. The disclosed concept also pertains to acoustic signature simulators. The disclosed concept further pertains to electrical distribution systems.
2. Background Information
Known switchgears, switchboards and motor control centers (MCCs) are custom designed and built. This makes it impossible to have a one-fit-all layout design of an acoustic sensing system for these power distribution systems.
There is no known cost effective technology and product to detect loose electrical connections in electrical distribution systems. An infrared imaging scan has been widely used to find such loose electrical connections, but this does not provide continuous (e.g., “24-7” or 24 hours a day, seven days a week) detection and monitoring, is limited to detecting only joints within view, and exposes the operator to potentially hazardous conditions.
Other known products employ temperature sensing at each electrical joint. However, this has not been widely adopted due to cost.
It is believed to be almost impossible to extract a loose electrical connection signature from both current and voltage due to the relatively small voltage drop across a loose electrical connection (except when this escalates into a major arc fault or arc flash event) except by monitoring voltage drops at each electrical connection.
U.S. Pat. No. 7,148,696 discloses that an acoustic signature is generated by an arc fault or a glowing contact. An acoustic sensor “listens” directly to signature noise generated by a fault, no matter what type of electrical load is present or in what kind of environment in which the fault is generated. The acoustic noise generated by an arc fault or a glowing contact has an acoustic signal at one or more specific wavelengths that is (are) directly related to either the basic characteristics of, for example, the arc and its resonance frequency or the AC power source modulated frequency and its harmonics. The acoustic signal of an arc fault is detected by an acoustic sensor. A resulting trip signal is sent to a trip mechanism to, for example, trip open separable contacts, in order to interrupt the arc fault.
U.S. Pat. No. 7,411,403 discloses a circuit breaker that detects a loose electrical connection condition of a power circuit. The circuit breaker includes first and second lugs, and first and second acoustic couplers acoustically coupled to the power circuit. An acoustic generator is coupled to the second acoustic coupler and generates a first acoustic signal to the power circuit from the second acoustic coupler. An acoustic sensor is coupled to the first acoustic coupler and has a second acoustic signal which is operatively associated with the loose electrical connection condition. The acoustic sensor outputs a sensed acoustic signal. A circuit cooperates with the acoustic generator to generate the first acoustic signal, input the sensed acoustic signal, and detect the loose electrical connection condition therefrom. The circuit can output a trip signal to a trip mechanism upon detecting an electrical conductivity fault from the sensed acoustic signal.
There is room for improvement in electrical distribution systems.